Dutch Elm Disease is caused by an aggressive fungus that kills trees regardless of their health. It is considered the most costly shade tree disease ever and will remain active in a community as long is there are susceptible trees. The pathogenic fungus (Ophiostoma-ulmi) invades the water transporting vessels and produces toxins to which the tree responds. The primary defense mechanisms of the tree include the production of gums and internal growiths designed to block the advance of the fungus. The combonation of the toxins and the defense mechanisms of the tree inhibit water flow to the crown, which causes wilting and ultimately tree death.
What are the symptoms of Dutch Elm Disease?
Dutch Elm Disease symptoms begin to develop 4-6 weeks after infection. The first noticeable symptom that results from the fungal occupation of the water conduction vessels is wilting or "flagging" of one or more branches, usually starting at the branch tip. Leaves on infected branches turn dull green to yellow, curl, and become dry and brittle. As the infection spreads the wook beneath the bark displays a brown discoloration.
How does the Disease infect healthy trees?
The most common method of transmission of Dutch Elm Disease is on the bodies of the elm bark beetle. Female elm bark beetles lay their eggs beneath the bark of dead and dying elm trees. If the elm is infected with Dutch Elm Disease the newly hatched beetles will emerge from the tree carrying thedeadly fungus on their bodies. The beetles fly to healthy trees to feed in 2-4 year old branches and therby spread the disease.
2-3 generations of bark beetles hatch every year
thousands of beetles may hatch from a single tree
Besides beetle transmission, Dutch Elm Disease may also spread through grafted roots. When elms grow in close proximity to each other (crowns touching), their roots come into contact and graft together. This common root system provides the fungus with a path to spread through an entire stand of healthy elms very quickly.
Arbotect does not prevent root graft infection. Thus if a diseased elm is close to a healthy elm, the roots must be physically severed to a depth of 3 feet in most soils.
What can I do if my tree is already infected?
Most infected elms cannot be saved. In rare cases, if the fungus has not moved into the root system, physically cutting out the infected portions of the tre, with a process called tracing can save the elm.
How does the injection work?
Arbotect protects agains Dutch Elm Disease infections by coating the vascular tissue of the elm where the fungus grows. Thus, it is important the chemical becomes systemically distributed throughout the 2-4 year old branches in which the insects feed and spread infections. The only method proven to accomplish this is a macro-injection of th proper dosage of fungicide into the root flares of the tree. Injections higher up the trunk are not as effective because they do not provide complete and even distribution of the chemical.
Which trees should be protected?
The best candidates for fungicide protection are healthy, valuable elms. The injection will provide protection against beetle carriers for up to three growing seasons at this time another injection is required.